ES2228813T3 - PIPE HEATING OVEN. - Google Patents

Abstract

Heating system, especially installation (1) for thermal processes, with a wall arrangement (2), which limits at least partially an inner chamber (3), which can be heated, with tubes (4) heaters for the conduction of one or more fluids, which must be heated, arranged in the chamber (3) essentially parallel to each other, with burners (6), which, for heating the inner chamber (3), are arranged transverse in relation to the tubes (4) heaters and oriented with their jet of air and fuel against an opposite part (21) of the wall arrangement (2), at the same time, that the tubes (4) are arranged in a row (10), which has at least two sections (11, 12) of rows of tubes, which are not oriented parallel to each other and that form an angle to each other, which opens away from the burners (6).

Description

Tube heating oven.

The invention relates to a system of heating, especially an installation for thermal processes in which a product stream is indirectly heated in tubes

In installations for thermal processes, indirectly heat fluids, often subjected to pressure, at the same time, that thermal energy is harnessed for a heating, a phase transformation, as heat of reaction (endothermic reaction) or for several of these effects. The fluids are conducted in heating tubes, which are loaded into the Most cases up to its thermal limit. In this procedure local overheating should not occur.

Through the document EP-A-0 079 980 a boiler is known for hot water, reheated water or steam with gas or household diesel oil. The boiler is formed by a combustion chamber built in the shape of a cone trunk. At its smallest end a burner is arranged, which makes a flame penetrate axially in the combustion chamber. The flame is surrounded by arranged tubes as concentric rings relative to the central axis of the burner. Another group of annular tubes with a larger diameter is arranged concentrically in relation to the first group of annular tubes, of way, that seen in longitudinal section an arrangement is formed zigzag. However, it is oriented parallel to the longitudinal axis of the burner.

Figures 7 and 8 show installations 1 for thermal processes known in practice. The installations 1 for thermal processes always have an inner chamber surrounded for example by a wall 2 of masonry of the oven in which they are 4 heating tubes arranged. For the warming of these burners 6 are arranged in holes in the wall 2 of the oven. The heater tubes 4 are arranged in the embodiment according to Figure 7 vertically and next to each other in rows, of so that between rows 7 of tubes a pair is formed in pairs passage 8. Burners 6 print fuel and air a impulse is axial output, which propagate to passage 8, at the same time, that heat is transmitted to the 4 heater tubes, above all, by the radiation of the flames and the gas. The radiation coming from the wall 2 of the furnace has an irregular impact on the 4 heater tubes.

A relatively heat transfer is obtained little. In addition, this provision is not prepared for use of burners with flameless oxidation, which generate zones relatively large reducing atmosphere harmful to 4 heater tubes.

In installation 1 for thermal processes of the figure 8 the heater pipes 4 are arranged in a row approximately in the center of the inner chamber 3. In holes 6 'rotary burners are provided on the wall 2 of the oven, which print to fuels and combustion air provided a essentially radial output pulse. The flame and the zones hot from the wall 2 of the oven generate a hot zone, which transmits most of the flame energy by radiation to The pipes 4 heaters. Areas with a large intensity of radiation are small, so you need to install a quantity large 6 'rotating burners.

Starting from here, the objective of the invention is create an arrangement, which makes possible a uniform heating of the tubes avoiding overheating of the tubes. The same On time, you should get as compact a layout as possible.

The burners generate on the opposite wall, with the arrangement according to the invention of the burners and the tubes heaters, a large area of high temperature, found in radiation exchange without the formation of shadows with the tubes heaters The energy is transmitted uniformly by solid body radiation (wall - tube), by gas radiation (reaction zone - tube) and by convection (combustion products that have reacted fully - tubes).

Burners print to the fuel jet and outgoing air preferably a large axial output pulse. This is preferably so large, that the jet reaches the wall opposite and generates a hot spot / zone on it. Burners they can have exit holes for the fuel mixture and air or separate outlet holes for fuel and air. This gives heat radiation to the heating tubes.

If burners are used, work according to the principle of flameless oxidation, no tips are formed temperature in the vicinity of the burners, so that the sections of rows of pipes arranged at an angle can be arrange relatively close in front of the burner. The recirculation in a large space of flue gases makes possible, especially in the case of flameless oxidation, a optimal reduction of NO_ {x} emission, even with a maximum preheating of the air. The relatively reducing areas large, that form, do not come into contact, due to the arrangement of the tubes, with the heating tubes. The disposition of the tubes also makes possible a compact construction of the installation and a large heat transfer without tips temperature in the heating tubes.

In addition, the appropriate burners for the flameless oxidation also make the use of problematic or combustible fuels with a composition variant, which would generally create stability problems in the flame formation

Other details of advantageous embodiments are subject to the drawing, description or claims subordinates

Execution examples are represented in the drawing of the invention In it they show:

Figure 1, in a schematic representation in horizontal section, an installation for thermal processes with the arrangement according to the invention of the burners and the tubes heaters

Figure 2, in a sectional representation horizontal, a modified form of installation execution for thermal processes

Figure 3, in a schematic view in perspective, the installation for thermal processes according to figure 1 or figure 2.

Figure 4, a modified embodiment of The installation for thermal processes.

Figure 5, another modified embodiment of the installation for thermal processes.

Figure 6, in a schematic representation in section and principle, a burner of the installation for processes thermal.

Figures 7 and 8 also represent installations for thermal processes according to the state of the technique.

An installation 1 is shown in figure 1 for thermal processes with a wall 2 (2a, 2b) of oven masonry, which limits an oven chamber 3 and forms a wall layout In the chamber 3 of the oven are arranged 4 heater tubes in which a fluid circulates, which must be heated or maintained at a high temperature. The fluid can be exposed to chemical transformations on its way through the 4 heater tubes.

The 4 heater tubes are arranged, as shows figure 1, with its parallel and spaced axes in a row 10 shaped like a zigzag. Groups 11 and 12 of tubes 4 heaters always form a section of pipe row, that are not aligned parallel to each other and that form a non-zero angle, preferably acute (for example 30º ... 80º). The angles formed by sections 11, 12 of pipes are alternately open towards one or the other wall 2a, 2b of the oven mutually facing each other. In the example of execution according to the figure 1, the row sections formed by groups 11, 12 are themselves straight, at the same time, that the sections of group 11 are parallel each. Also the row sections of group 12 are straight and parallel to each other in this example. However, it is also possible arrange the heating tubes 4 in such a way that the sections of row of groups 11 and 12 are curved or wavy.

For heating the pipes 4 heaters burners 6a, 6b located in corresponding holes are provided of the wall 2a., respectively 2b of the oven. In the way of execution according to figure 1, the burners 6a, 6b are burners Flameless oxidation preparations. They generate a jet of fuel and air, ie a jet 14a, quantitative 14b with axial output pulse oriented against the wall 2a, 2b of the oven opposite in each case. In the exit of the burners it is avoided, by means of a corresponding configuration from the point of view of circulation, the stabilization of a flame.

The jet 14a, 14b quantitative from the burner 6a, 6b is always between two tubes 4 heaters adjacent, of which one belongs to group 11 and the other to the group 12. Then a recirculation current is formed in a space large represented in figure 1 with arrows 15 at the same time that a zone is formed between the rows of groups 11, 12 16 large reaction.

The burners 6a, 6b are constructed as recovery burners or regenerative burners, which allow a large preheating of the air. An example is represented in figure 6 a scheme of principle of a recovery burner 6. This has a central fuel inlet pipe 17, which Let the fuel out with an axial output pulse. In addition, the burner 6 has an air inlet 18, which also confers on the outgoing combustion air an axial output pulse. The entrance 18 of air is through a recovery tube 19 in heat exchange with a jet of exhaust gas, which is extracted of the furnace chamber in counter current by means of a pipe 20 exhaust gas. The recovery tube 19 is an exchanger of hot. With the evacuation of the exhaust gases by means of burners 6 is achieved, that the regulation zones of the temperature influence little each other.

As Figure 3 shows, they can be arranged in each wall 2a, 2b of the oven a row with several burners 6, at same time, that burners 6 (6a, 6b) always generate a output pulse oriented transversely in relation to 4 heater tubes and are arranged in groups in rows oriented parallel to the tubes 4 heaters. The burners 6 are can be arranged with equal separations or with separations unequal For example, in the case of a fluid jet directed downwards a first zone can be provided higher number of burners (burner density) to heat first of all the jet of incoming fluid quickly, while in zones 2, 3 below are enough less 6 burners to maintain the temperature reached.

Additionally, 6 '' burners can be provided oriented parallel to the 4 burner tubes and which have This is an output pulse parallel to these 4 heater tubes. These heaters are preferably arranged in zigzag above, respectively below zones 16, limited approximately in the shape of a triangle by groups 11, 12 (figure 1) of the oven chamber 3. Might be useful for the start of the installation, that is to say for a first heating, due to the fact that they heat parallel to the tubes 4 heaters and then disconnected, are switched to Flameless oxidation or keep running. In a way of preferred execution the 6 '' burners are burners equipped with flame maintainers, which produce a flame, while the burners 6a, 6b are burners without flame keepers preparations for flameless oxidation, which only connect in been hot However, if necessary, it can be foreseen as burners 6a, 6b switchable burners, which first they work with flame for ignition and that, once reached the necessary temperature, they go into operation without flame.

Installation 1 for thermal processes described So far it works as follows:

Burners 6a, 6b generate during the running a jet of fuel and air transverse to the tubes 4 heaters approximately perpendicular to the wall 6a, 6b from the oven and directed towards the opposite wall 2a, 2b of the oven. He jet passes through tubes 4 adjacent heaters and reaches the oxidation zone 16 in which flameless oxidation takes place. The heat released here comes with the gas jet to the wall 2b, 2a of the oven in which a corresponding zone 21 is formed very hot. The heat radiation coming from this zone 21 affects, same as heat radiation from zone 16 of oxidation, in the tubes 4 heaters without shielding. The heat distribution is relatively uniform, that is, all 4 heater tubes receive approximately the same amount of heat

Because of the momentum, directed alternately in opposite directions, of the burners 6a, 6b a circulation in a large space, as indicated by arrows 15. Recirculation in a large space always covers tubes 4 heaters of each group 11, 12, which results in a heat transmission by uniform convection. Pipes 4 heaters are outside the oxidation zone 16, in which a reducing atmosphere reigns, which avoids the corresponding tube wear.

The 4 heater tubes are arranged in the Execution example shown in Figure 1 with separations mutual equals in general. By means of the number of tubes heaters, their separations and the angle between them sections of groups 11, 12 can be influenced in a defined way in The heat distribution between the 4 heater tubes. Through of the angle, of the quantity and the separation of the tubes heaters can determine the relationship between the surface of the wall 2 of the oven and the surface of the tubes, trying to preference to achieve approximately equality between the surface of the tubes and the furnace wall surface.

The burners 6 can be regulated with preference as well as connected and disconnected individually. From this way can be further influenced in a definite way in the heat distribution in oven chamber 3.

A form of Modified execution of installation 1 for thermal processes according to the invention. Instead of the burners intended for flameless oxidation burners 6 are planned here, which launch a flame against the corresponding wall 2a, 2b opposite the oven. The Zigzag arrangement of the 4 heater tubes and the traffic conditions in a large space are without However, analogous to those of the embodiment according to Figure 1. You can also provide additional 6 '' burners, as emerges from figure 3.

As Figure 4 shows, it is also possible arrange the 4 heater tubes, both with flame burners, as also with flameless burners, in a wavy row. This row also has sections formed by groups 11, 12 of tubes 4 heaters not aligned parallel to each other. Without However, in accordance with the form of execution according to the Figures 1 and 2, groups 11 and 12 preferably have the same number of tubes 4 heaters at the same time as the separations between the tubes 4 heaters of group 11 and the tubes 4 heaters of group 12 increases from burner 6 corresponding to the opposite wall of the oven. It is not necessary, that the increase in separation is linear. It is also not necessary, that the separations between the tubes 4 heaters are equidistant.

As Figure 5 shows, they can be foreseen in if necessary tubes 4 'additional heaters, which serve by example as overheating pipes, which are assigned to another phase of the process or that fundamentally must meet conditions other than those of the 4 heater tubes. However, it try to arrange the additional 4 'tubes in such a way that essentially influence the described operation of the 1 installation for thermal processes.

An installation 1 for thermal processes has 4 heater tubes arranged in a wavy row in a chamber of oven. Both in the "ridges" and in the "valleys" of the Ripple burners are provided, which generate a jet of gas directed against the opposite wall of the oven. The heat of radiation from the oven wall and the reaction zone (heat of combustion) Heats the heating tubes.

Claims (8)

1. Heating system, especially installation (1) for thermal processes, with an arrangement (2) of wall, which at least partially limits an inner chamber (3), which can be heated, with tubes (4) conduction heaters of one or several fluids, which must be heated, arranged in the chamber (3) essentially parallel to each other, with burners (6), which, for heating the inner chamber (3), are arranged transversal with respect to the tubes (4) heaters and oriented with its jet of air and fuel against an opposite part (21) of the wall arrangement (2) at the same time as the pipes (4) they are arranged in a row (10), which has at least two sections (11, 12) of rows of tubes, which are not oriented in parallel each other and that form an angle to each other, which opens away from the burners (6). 2. Heating system according to claim 1, characterized in that the pipes are arranged spaced apart from each other in a row (10) in the form of a zig-zag, corrugated or in the form of a meander, which extends between two walls (2a, 2b) parallel to each other of the wall arrangement (2). 3. Heating system according to claim 1, characterized in that the burners are aligned in such a way that the gas stream from the corresponding burner (6) is oriented between two mutually adjacent heater tubes (4) towards an essentially free area of the inner chamber 4. Heating system according to claim 1, characterized in that several of the burners (6) are arranged in a group (6a), in which they are arranged in a row and are aligned parallel to each other. 5. Heating system according to claim 1, characterized in that the additional burners (6 '') are oriented essentially parallel to the heating pipes (4). 6. Heating system according to claim 1, characterized in that the burners (6) are provided with a device for preheating the air. 7. Heating system according to claim 1, characterized in that the burners (6) are prepared for the creation of the conditions under which the flameless oxidation of the fuel injected into the inner chamber (3) occurs. 8. Heating system according to claim 1, characterized in that the burners print the fuel and combustion air introduced into the inner chamber (3) a predominantly axial output pulse with a small or zero rotation.